No abstract

Polytetrafluoroethylene (PTFE) was treated in a low-power plasma using a series of feed gases (O 2 , Ar, N 2 and NH 3 ) and the resulting surface modifications were evaluated by x-ray photoelectron spectroscopy, static secondary ion mass spectroscopy, dynamic contact angle measurements and atomic force microscopy. All plasma treatments caused light etching, but the nature and extent of chemical modification varied considerably. Fluorine depletion of the surface was affected most efficiently by Ar and least effectively by O 2 plasma. New functionalities were introduced to the surface either from plasma derivatives of the feed gases or by post-treatment exposure to moist air; Ar, N 2 and NH 3 were more effective than O 2 in this respect. The wettability of virgin and plasma-treated materials in phosphate-buffered saline solution (PBS) and 1-bromonaphthalene was studied, and the observations are discussed in a framework that correlates contact-angle hysteresis with surface chemistry in a semi-quantitative manner. In Part II of this work, further changes of the surface chemistry and wettability of virgin and plasma-treated materials arising due to storage in PBS or air are described.

No abstract

In order to ascertain the tamponade effect of air and silicone oil we examined the contact angles subtended by ex vivo human retina, Teflon and Perspex to find a suitable experimental material which would mimic the surface properties of the retina at a three-phase interface. Using the captive bubble technique to measure the contact angle, it was found that air subtended a larger contact angle (38.8 degrees) with the retina than did silicone oil (18.2 degrees). On coating the Perspex surface with protein (PCP), it was observed that the surface properties were modified such that PCP subtended contact angles with air (43.0 degrees) and silicone oil (16.4 degrees) similar to those subtended by ex vivo human retina. Using PCP as an experimental material that mimics ex vivo human retina, spherical chambers were employed in order to examine qualitatively and to quantify the arc of contact obtained with air and silicone oil. It was found that air gave a greater arc of contact for the same percentage fill than silicone oil.

No abstract